PURPOSE: To easily recover noble metals and more particularly palladium at a high recovery rate by treating a soln. contg. compds. of the noble metals at a specific temp. by using a reducing agent in the presence of a specific amt. of an assistant contg. primary or secondary amino groups.
CONSTITUTION: The soln. or mixture contg. the compds. of the noble metals generated from an oxidation reaction using an alkyl nitrite is treated with the reducing agent, by which the noble metals are recovered in the form of metals or their salts. The assistant which contains the primary or secondary amino groups reacting with nitrous acid or is capable of forming these groups under reaction conditions is added to the soln. or mixture during the time of the reduction treatment. The amt. of the assistant to be added is specified to 0.001 to 0.5 times, more preferably 0.01 to 0.4 times, more particularly preferably 0.05 to 0.3 times the amt. of the soln. or the mixture. The treatment temp. of this time is specified to 0 to 100°C, more preferably 20 to 90°C, more particularly preferably 40 to 80°C. As a result, the reduced noble metals of the grain size suitable for filtration may be obtd. and, if necessary, the noble metals may be converted to the noble metal compsns. of high catalyst activity by treating the same with an acid.
AREKUSANDAA KURAUZENAA
HAINTSU URURIHI BURANKU
